3.73 To 4.10 Gear Ratio Swap

gandolphxx · Jun 19, 2002

Well, in for a dime, in for a dollar - I am swapping the 3.73 gears in my K2500 to 4.10's to get the full performance from the 8.1L engine, I am tired of the transmission hunting on the road.

The rear is easy, the front has to be completely taken apart, and will have new seals and bearings, should be like new.

4wheelparts is doing the job next week, about 2K and I now own a HPP3 to change the gear ratio on the custom chip.

steelheadchaser · Jun 19, 2002

Big move there Gand! Is this strictly a ring/pinion swap or are you going to install different diffs while its apart? How big a change do you think you'll see with trap speed and E.T.s ?

simtechray · Jun 19, 2002

I'm not far behind ya.
After installing my new tires these 3.73's just don't cut it anymore. I was considering a gear swap before the tires but now its definate.
Do you have the G80 (locker) option gandolphxx?
I was wondering if the G80 part number is the same for both gear ratios (3.73 + 4.10).

gandolphxx · Jun 19, 2002

Steelheadchaser - just the gears, considered the Auburn to replace the G80, but they don't make one for the 14 bolt 10.5 rearend, so that will stay. The K2500 already has the largest rearend that GM makes [or damn near it] so it is fine, just the ratio was wrong from day one - 3.73 is way to low for the engine power curve.

SimTechRay, G80 should be the same, for either.

gandolphxx · Jun 27, 2002

well its done, 4.10 and it still runs in 2HI, Auto and 4HI, haven't tried 4LO yet - trying [barely] to follow breakin procedure

It is a nice improvement on the highway, haven't tried a power start yet. Cost more than I thought since I had to use GM gear and pinion in the rearend, something changed between '01 and '02 - a little heavier duty - just as well.

Now to master the HPP3 and reset the PCM without messing up the custom stuff

Then the real test at the track. >:D

simtechray · Jun 27, 2002

gandolphxx said:
I had to use GM gear and pinion in the rearend

Did you use a site sponser ? >:D

?
What was the final tally, if ya don't mind me asking.
Maybe my little 10 bolt will come out cheaper

gandolphxx · Jun 27, 2002

SimTechRay said:
Did you use a site sponser ? ?
What was the final tally, if ya don't mind me asking.
Maybe my little 10 bolt will come out cheaper ?

No, the truck was in pieces when they discovered it, bought locally, otherwise I would have.

Just a note, my dealer had his chance, wimped all over the place, mumbled about warranty and speedo problems, sheesh.

final tally about $2200 before discount - and I supplied the Redline, wouldn't have anything else in there. That doesn't count the HPP3 to reset the PCM

Victor · Jun 30, 2002

Please help me here AV people. I am about to purchase my first AV this week, but I am having trouble with one decision.
One of the Av's has a 3.73 ratio and the other has the 4.10 ratio. Both are 1500's and I am wondering what the bug difference is. What will be the difference in gas mileage

( That's my biggest concern ).

Any help will be greatly appreciated,

Thanks,
Vic

LazKat · Jun 30, 2002

Victor,

I'll just jump in here at this one. I thought the 1500 w/ 3.73s seemed kind of sluggish when I first test drove it. I tried one with 4.10s and immediately noticed the difference. Needless to say mine has 4.10s - and I had a helluva time finding one just like I wanted. On the mileage - I get 14/15 city, 18/19 highway - and better takeoffs from a standing start. I'm not racing light-to-light but do like the responsiveness.

gandolphxx · Jun 30, 2002

UPDATE: 230 miles on the new gears and the PCM is finally reset to know what is there. Fabulous - my engine practically hugged me, these 4.10's are a natural with the 8.1L, plenty of power, no shift hunting on the highway - keeps that monster right in the sweet zone, and great startup - now I need ET Streets. >:D

marc_w · Jul 1, 2002

gandolphxx said:
The K2500 already has the largest rearend that GM makes [or damn near it] so it is fine, just the ratio was wrong from day one - 3.73 is way to low for the engine power curve.

The 8.1 has a power curve??

gandolphxx · Jul 1, 2002

You bet it does: lots, more, and OMG

marc_w · Jul 1, 2002

Are you sure that's not the gas-useage-curve? :-X

gandolphxx · Jul 1, 2002

Yes that too - que sera, sera

02_2500avalanche · Jan 12, 2003

You can't just change the rear end gears you have to change the front aswell?

Alex

steelheadchaser · Jan 12, 2003

02_2500avalanche said:
You can't just ?change the rear end gears you have to change the front aswell?

Alex

Sorry, Alex. Both diffs have to have the same gear ratio in a 4x4.

mrosenfield · Jan 23, 2003

Bought and S-10 Blazer new back about 17 years ago- the dealer wouldn't release it to me because the front end did weird things when in 4WD. The sold me another one, and spent 2 weeks to discover that the factory had put different gear ratios front and rear!
Just a bit of ancient history...

lust4speed · Jan 28, 2003

Well, my RCD lift is done along with the 315x70R17 tires. ?I'm really surprised that the 3.73's don't feel that bad pulling the big rubber. ?I actually notice more of a performance decline with the brakes than with the acceleration. ?Speedo is now slow about 4 mph at 60 - it was 1 mph fast according to the GPS. ?But I'm sure that the higher ratio will catch up with me when I'm towing. ?So here's another question that I searched for without results: Why not go to 4.56 gears since the installation dollars are the same as the 4.11 replacements? ?According to the gear chart, the rpm's would only be slightly higher with 35" tires than the 4.11 option with stock tires. ?The only complaint I had while 4-wheeling before was the lack of compression braking coming down the steep ones, and it seems that the 4.56's would help that a little also.

11H · Feb 13, 2003

lust4speed,,,

The only thing I could think of, is that if you do the 4.56's, you will almost certainly have to run a good size diameter tire; other than stock...

OR

265/70/R17 = "she'll be singin' 'round the mountain when she comes, she'll be singin' ..... "

11H

lust4speed · Feb 13, 2003

Well, we did a little towing out to the dunes with the ATV's on the trailer. ?Total towed weight was ?only about 2,900 pounds. ?We did have to pull the pass in third gear, but other than that, everything went smooth. ?Taking off from a standstill even with the trailer proved to still be impressive, but after first gear was done, things got pretty mundane. ?Again the 315's are about 34.5" in diameter, and unless someone can post a reason for staying with the 4.10's, I think that my choice will be the 4.56's. ?This is a 1500 by the way. ?The only concern was I remember someone saying that due to the size of the pinion gear, the 4.56's were not as strong.

EVANBLANC · Apr 7, 2014

Hey,
I've got an 08 w/ 4" lift and 33s. I am having her re geared next monday, but still havent decided on what to go with. I am leaning toward a 4.56. I do not care whatsoever what my gas mileage is. That being said, what would you all recommend with my configuration?? My truck will also be fully dyno tuned after the swap.
Thanks!

ohiobellboy · Apr 7, 2014

EVANBLANC said:
Hey,
I've got an 08 w/ 4" lift and 33s. I am having her re geared next monday, but still havent decided on what to go with. I am leaning toward a 4.56. I do not care whatsoever what my gas mileage is. That being said, what would you all recommend with my configuration?? My truck will also be fully dyno tuned after the swap.
Thanks!

This thread is 11 years old. I really don't expect a response from the OP

MyBigToy · Apr 7, 2014

EVANBLANC said:
Hey,
I've got an 08 w/ 4" lift and 33s. I am having her re geared next monday, but still havent decided on what to go with. I am leaning toward a 4.56. I do not care whatsoever what my gas mileage is. That being said, what would you all recommend with my configuration?? My truck will also be fully dyno tuned after the swap.
Thanks!

OBB is correct - gandolphxx hasn't been around for at least 9 years.

As far as gears - 4.10s are fine for 33s. 4.56s are better suited for 35s. If you really want maximum acceleration and don't care about gas mileage and higher rpms on the highway, the 4.56s will give you that.

avalonandl · Apr 8, 2014

I would think the 4.10 would do you fine. 4.56 is very radical and a full 10% reduction from a 4.10.

Avalon

raiderron · Apr 8, 2014

Since you guys are on the subject of the 4.10 gears, do you have any idea what kind of in town and highway mileage I can expect with mine? 02 Z71 with 5.3 engine, 265/70R17 tires. I don't romp on the fuel or anything unless I need to when passing. I just got the rig about 2-3 weeks ago and just topped off the fuel yesterday and reset the trip meter so I can get an idea for fuel mileage. The best part is what I do for a living. I don't have to drive to work. I live at and manage a storage facility here in Eugene, Oregon so work is a walk through a door away. Can typically fill my tank and if I hang at home mostly I can go 1-1 1/2 months between fill ups. thanks in advance for any info. :wave:

3.73 To 4.10 Gear Ratio Swap

Victor

11H

New Member